From 1900-2010, freshwater fish species in North America went extinct at a rate 877 times faster than the rate found in the fossil record, while estimates indicate the rate may double between now and 2050. This new information comes from a U.S. Geological Survey study to be published in the September issue of the journal BioScience. In the fossil record, one freshwater fish species goes extinct every 3 million years, but North America lost 39 species and 18 subspecies between 1898 and 2006. Based on current trends in threatened and endangered fish species, researchers estimate that an additional 53-86 species of freshwater fish may be extinct by the year 2050. Since the first assessment of extinct North American freshwater fishes in 1989, the number of extinct fishes increased by 25 percent
Freshwater fish are fish that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 0.05%. These environments differ from marine conditions in many ways, the most obvious being the difference in levels of salinity. To survive fresh water, the fish need a range of physiological adaptations. 41% of all known species of fish are found in fresh water.
"Another cause of extinction can be a change in a fish's food chain, which is what may have happened to the harelip sucker, a really cool fish that used to live in seven states throughout the Ohio River basin," said Burkhead. "It was a snail-eating specialist with cleft lips that used to pluck snails off river bottoms and manipulate the snail in its mouth in order to suck out the snail's soft parts, perhaps making little popping sounds. Sadly, snails are highly sensitive to excessive sedimentation and in the late nineteenth century, large amounts of topsoil were washing into rivers along with sewage and industrial effluents from cities. This likely caused snails to decline, which may have been what drove the fish to extinction."
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